1. Technical Field of the Invention
This invention relates generally to wireless communication systems and more particularly to wireless communications within such systems.
2. Description of Related Art
Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards including, but not limited to, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), radio frequency identification (RFID), Enhanced Data rates for GSM Evolution (EDGE), General Packet Radio Service (GPRS), WCDMA, LTE (Long Term Evolution), WiMAX (worldwide interoperability for microwave access), and/or variations thereof.
Depending on the type of wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, RFID reader, RFID tag, et cetera communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of the plurality of radio frequency (RF) carriers of the wireless communication system or a particular RF frequency for some systems) and communicate over that channel(s). For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via the public switch telephone network, via the Internet, and/or via some other wide area network.
For each wireless communication device to participate in wireless communications, it includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for in-home and/or in-building wireless communication networks, RF modem, etc.). As is known, the receiver is coupled to an antenna and includes a low noise amplifier, one or more intermediate frequency stages, a filtering stage, and a data recovery stage. The low noise amplifier receives inbound RF signals via the antenna and amplifies then. The one or more intermediate frequency stages mix the amplified RF signals with one or more local oscillations to convert the amplified RF signal into baseband signals or intermediate frequency (IF) signals. The filtering stage filters the baseband signals or the IF signals to attenuate unwanted out of band signals to produce filtered signals. The data recovery stage recovers data from the filtered signals in accordance with the particular wireless communication standard.
As is also known, the transmitter includes a data modulation stage, one or more intermediate frequency stages, and a power amplifier. The data modulation stage converts data into baseband signals in accordance with a particular wireless communication standard. The one or more intermediate frequency stages mix the baseband signals with one or more local oscillations to produce RF signals. The power amplifier amplifies the RF signals prior to transmission via an antenna.
Whether wireless communication devices communicate directly or indirectly, the wireless communication channel, or channels, supporting the communication introduce errors that, if left uncorrected, would compromise the integrity of the communication (e.g., packets are corrupted). The errors may result from one or more of noise, interference, path loss, multi-path fading, etc.
One solution to address the errors introduced by the channel(s) is to require the receiving device to acknowledge receipt of each packet. If a packet is not acknowledged, or the receiver requests a re-send, the transmitter resends the packet. While this addresses the error issue, it does so at the cost of reduced data throughput as a result of sending the packet one or more additional times plus it is difficult to use for real time communications (e.g., cellular voice communications).
Another solution is to use an error correction scheme (e.g., forward error correction, error-correcting code, etc.) where the data modulation stage of the transmitter encodes packets of data with corresponding error correction codes. On the receiver side, the data recovery stage uses, in a one-to-one relationship, an error correction code to recover data from the corresponding packet. As such, a packet with errors can be corrected without having to retransmit the packet based on the corresponding error correction code. If, however, the errors introduced by the channel exceed the capabilities of the error correction scheme, then the packet is lost or it has to be retransmitted. Neither is a desirable situation.
Therefore, a need exists for an encoder/decoder that provides a more robust error correction scheme.